Embodiments of the invention relate to systems and methods for metering energy in an energy distribution system. More particularly, embodiments of the invention relate to systems and methods for transmitting energy data by grouping mesh clusters to facility the transfer of the energy data from an energy sensing device to an energy management station.
Typically metering a particular point within an energy distribution system, such as an electrical distribution system, can be very costly and there are monetary and practical barriers to installing metering points. Some of these costs are external components such as potential transformers or current transformers, commissioning costs, measurement cabinet costs and installation costs.
A large installation cost associated with metering points is the cost and installation of communication wires including conduits for the communication wires. The availability of existing communication, cost of extending those communications, and the labor involved in running the communication wires can be prohibitive when evaluating the benefit of adding a new metering point. Alternatively, a metering point may be installed without any communication. In this case, someone must physically go to the meter and read a display, recording the energy values, and transporting this information to a central system. This approach is prone to human error in addition over time it can be an expensive communication method.
Another large installation cost associated with some metering points is the cost of providing an adequate power supply or separate power supply to the metering device. For example, a metering device may be monitoring at a point of a large voltage potential, while the device may be able to monitor the voltage potential, the control power required for the device must be at a significantly lower potential. Alternatively, a metering device may be monitoring a non-electrical quantity such as the output of a flow meter. There may not be a conventional power supply for the metering device accessible; in which case, additional installation expense is required to provide control power to the metering device.
A further installation cost associated with the physical mounting to the metering point. Typically metering points must be mounted into a measurement cabinet or measurement rack of some sort with a hole for a display or mounting screws to secure the metering device to the cabinet or rack. Many times display holes and screw holes must be made in the measurement cabinet or a measurement cabinet itself must be purchased further adding to the installation costs.
Typically, commissioning costs of energy metering points are relatively high. Often there is a need to have a factory representative on site to fully commission an energy metering system. In addition, there can be errors that are difficult to correct if the incorrect settings are sent to the metering device. An example of a commissioning error occurs when a monitoring device is set to an incorrect PT or CT ratio for electrical energy monitoring as incorrect primary measurements may be calculated from the secondary measurements. Another example may include setting up an incorrect value per pulse for the monitoring of a pulse output from another metering device. Additional commissioning costs include the manual setup for communication of monitoring devices with the energy metering system or SCADA software. Each metering point connected has to have communications configured at the metering point as well as at the software system. Any error in these configurations at either site can result in no communications and may require troubleshooting which further increases commissioning cost.
Typically the advantages of installing metering points closer to the supply of the energy outweigh the barriers; however, as the energy travels closer down the energy distribution system to the consumer and finally to the load, the costs of metering points often outweighs the benefits. However, there is a desire and financial benefit to monitoring energy distribution at additional metering points; especially further down the energy distribution system towards the load. When more information is known of the energy used, more can be done to reduce energy usage. There is a need to reduce the cost of ownership of an additional metering point within an energy management system. There is a need to reduce installation, commissioning, and costs of external components such as current transformers, potential transformers, and measurement cabinets. When these costs are reduced, the financial reward of energy cost analysis outweighs the reduced cost barriers of metering closer to each energy load. These additional metering points can assist in creating a clearer representation of energy costs throughout a facility and that information can assist the facility in reducing its energy costs.
In facilities, e.g. buildings or installations, where a significant amount of power is used among a variety of units, it would be desirable to allow the building owner to allocate energy costs to the different units, i.e. consumers, within the facility. For a commercial office building, these units may include the different tenants within the building or the common loads for the facility, such as the elevators or HVAC systems. For an industrial facility, these units may include the different production lines, machines or processes within the facility. As opposed to allocating costs based on a fixed or formulaic approach (such as pro-rata, e.g. dollars per square foot or based on the theoretical consumption of a process/machine), an allocation based on actual measurements using appropriate monitoring devices may result in more accurate and useful information as well as a more equitable cost distribution.
Both installation and ongoing, i.e. operational and maintenance, costs for these monitoring devices are important considerations in deciding whether a monitoring system is worth the investment. While monitoring devices may be read manually, which does not increase the installation cost, manual data collection may increase on-going/operational costs. Alternatively, monitoring devices may be interconnected and be automatically read via a communications link. However, typical communication links require wiring to interconnect the devices which increases the installation cost. In addition, a particular tenant in the building may wish to verify that they are being billed correctly by reading the energy meter or other energy monitoring device that is accumulating their energy usage. This may be a straightforward, although labor intensive and cumbersome, process with a typical energy meter which provides a display viewable by the tenant.
Emerging wireless mesh (or ad-hoc) networking technologies can be used to reduce the installation costs of monitoring devices while providing for automated data collection. Also called mesh topology or a mesh network, mesh is a network topology in which devices are connected with many redundant interconnections between network nodes. Effectively, each network node acts as a repeater/router with respect to received communications where the device is not the intended recipient in order to facilitate communications between devices across the network. Using wireless interconnections permits simpler and cost-effective implementation of mesh topologies wherein each device is a node and wirelessly interconnects with at least some of the other devices within its proximity using RF based links. Mesh networking technologies generally fall into two categories: high-speed, high bandwidth; and low speed, low bandwidth, low power. The first category of devices are typically more complex and costly that the second. Since energy monitoring does not typically require high speed/high bandwidth communication, the second category of devices is often sufficient in terms of data throughput.
Energy monitoring devices may include electrical energy meters that measure at least one of kWh, kVAh, kVARh, kW demand, kVA demand, kVAR demand, voltage, current, etc. Energy monitoring devices may also include devices that measure the consumption of water, air, gas and/or steam.